While planthoppers have been causing huge damages to rice crops in Thailand, Vietnam and China, rice crops in several areas in the Philippines have not been spared. In September 2010, several reports from the field were obtained and about 220 ha were seriously damaged. A diversity of inbred and hybrid varieties were grown in the areas. The inbred varieties were generally said to have moderate to intermediate resistance brown planthopper (BPH). Most the areas seemed to have suffered only “hopperburn” symptoms and virus infections were negligible.

Damages in most cases were in the later crop stages, although in Candon, Ilocos Sur, damages were observed at maximum tillering. Here the farmers were using high nitrogen inputs and weekly insecticide applications (Table 1).

Table 1: Summary of planthopper damages in the Philippines, September 2010.

The common feature among the farms that had suffered serious hopper damages was that they were sprayed with insecticides highly toxic to natural enemies, especially hymenopterans. These included cypermethrin, methomyl, thiamethoxam and methamidophos. It is well established that planthopper outbreaks are insecticide induced and it seemed clear that these cases of hopper outbreaks were due to insecticide misuse. These insecticides were also applied in the early crop stages. In Central Thailand where farmers used resurgence-causing insecticides, like cypermethrin and chlorpyrifos, outbreaks occurred in large areas (Read: Farmers’ insecticide selection). In the Philippines the high use of cypermethrin with known properties of making sprayed crops more vulnerable to hopper outbreaks is a concern as this can potentially increase and spread hopper problems. A consultation workshop with scientists from PhiRice and IRRI will be held in Los Baños on 27 September in Los Baños to explore for options and action plans to prevent the spread of the planthopper problems in the Philippines.